Question

A bullet dancer spins about a vertical axis at 60 rpm with his arm closed. Now he stretches his arms such that M.I increases by 50%. The new speed of revolution is

• A. $80rpm$
• B. $40rpm$
• C. $90rpm$
• D. $30rpm$

Answer 1

The correct option is B $40rpm$

Here,

As there is no net torque acting while she stretches her arms.

Hence,

$I_i{\omega }_i=I_f{\omega }_f$

$I\times 60=\frac{3I}{2}\times \omega$

$\omega =40rpm$

Option $\text{B}$ is the correct answer